To achieve voltages higher than that of a single cell, it is usual to form a stack of single fuel cells. In a fuel cell stack, a plurality of pipes, or manifolds, needs to be associated with the stack for supplying the fuel and oxidizing gases to the cells and recovering the spent gases.
In such arrangements, it is important to avoid the buildup of excessive voltages on the piping and excessive leakage currents in the piping which reduce the efficiency of the stack. Complicating these problems is the fact that some of the common electrolytes used in such cells, for example phosphoric acid, escape and tend to deposit on the inner walls of the piping and the insulation where they reduce the surface resistance of the insulation, which increases leakage current.
The present invention provides a fuel cell stack in which there is avoided the problem of voltage buildup in the piping and of leakage because of poor insulation.